Source Code Cross Referenced for ClassFieldInspector.java in  » Rule-Engine » drolls-Rule-Engine » org » drools » util » asm » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Rule Engine » drolls Rule Engine » org.drools.util.asm 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        package org.drools.util.asm;
002:
003:        /*
004:         * Copyright 2005 JBoss Inc
005:         * 
006:         * Licensed under the Apache License, Version 2.0 (the "License");
007:         * you may not use this file except in compliance with the License.
008:         * You may obtain a copy of the License at
009:         * 
010:         *      http://www.apache.org/licenses/LICENSE-2.0
011:         * 
012:         * Unless required by applicable law or agreed to in writing, software
013:         * distributed under the License is distributed on an "AS IS" BASIS,
014:         * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015:         * See the License for the specific language governing permissions and
016:         * limitations under the License.
017:         */
018:
019:        import java.beans.Introspector;
020:        import java.io.IOException;
021:        import java.io.InputStream;
022:        import java.lang.reflect.Method;
023:        import java.lang.reflect.Modifier;
024:        import java.util.ArrayList;
025:        import java.util.HashMap;
026:        import java.util.HashSet;
027:        import java.util.List;
028:        import java.util.Map;
029:        import java.util.Set;
030:
031:        import org.drools.asm.AnnotationVisitor;
032:        import org.drools.asm.Attribute;
033:        import org.drools.asm.ClassReader;
034:        import org.drools.asm.ClassVisitor;
035:        import org.drools.asm.FieldVisitor;
036:        import org.drools.asm.MethodVisitor;
037:        import org.drools.asm.Opcodes;
038:
039:        /**
040:         * Visit a POJO user class, and extract the property getter methods that are public, in the 
041:         * order in which they are declared actually in the class itself (not using introspection).
042:         * 
043:         * This may be enhanced in the future to allow annotations or perhaps external meta data
044:         * configure the order of the indexes, as this may provide fine tuning options in special cases.
045:         * 
046:         * @author Michael Neale
047:         */
048:        public class ClassFieldInspector {
049:
050:            private final List methods = new ArrayList();
051:            private final Map fieldNames = new HashMap();
052:            private final Map fieldTypes = new HashMap();
053:            private final Map methodNames = new HashMap();
054:            private final Set nonGetters = new HashSet();
055:
056:            /**
057:             * @param clazz The class that the fields to be shadowed are extracted for.
058:             * @throws IOException
059:             */
060:            public ClassFieldInspector(final Class clazz) throws IOException {
061:                this (clazz, true);
062:            }
063:
064:            public ClassFieldInspector(final Class clazz,
065:                    final boolean includeFinalMethods) throws IOException {
066:                final String name = getResourcePath(clazz);
067:                final InputStream stream = clazz.getResourceAsStream(name);
068:
069:                if (stream != null) {
070:                    processClassWithByteCode(clazz, stream, includeFinalMethods);
071:                } else {
072:                    processClassWithoutByteCode(clazz, includeFinalMethods);
073:                }
074:            }
075:
076:            /** Walk up the inheritance hierarchy recursively, reading in fields */
077:            private void processClassWithByteCode(final Class clazz,
078:                    final InputStream stream, final boolean includeFinalMethods)
079:                    throws IOException {
080:
081:                final ClassReader reader = new ClassReader(stream);
082:                final ClassFieldVisitor visitor = new ClassFieldVisitor(clazz,
083:                        includeFinalMethods, this );
084:                reader.accept(visitor, false);
085:                if (clazz.getSuperclass() != null) {
086:                    final String name = getResourcePath(clazz.getSuperclass());
087:                    final InputStream parentStream = clazz
088:                            .getResourceAsStream(name);
089:                    if (parentStream != null) {
090:                        processClassWithByteCode(clazz.getSuperclass(),
091:                                parentStream, includeFinalMethods);
092:                    } else {
093:                        processClassWithoutByteCode(clazz.getSuperclass(),
094:                                includeFinalMethods);
095:                    }
096:                }
097:                if (clazz.isInterface()) {
098:                    final Class[] interfaces = clazz.getInterfaces();
099:                    for (int i = 0; i < interfaces.length; i++) {
100:                        final String name = getResourcePath(interfaces[i]);
101:                        final InputStream parentStream = clazz
102:                                .getResourceAsStream(name);
103:                        if (parentStream != null) {
104:                            processClassWithByteCode(interfaces[i],
105:                                    parentStream, includeFinalMethods);
106:                        } else {
107:                            processClassWithoutByteCode(interfaces[i],
108:                                    includeFinalMethods);
109:                        }
110:                    }
111:                }
112:            }
113:
114:            private void processClassWithoutByteCode(final Class clazz,
115:                    final boolean includeFinalMethods) {
116:                final Method[] methods = clazz.getMethods();
117:                for (int i = 0; i < methods.length; i++) {
118:
119:                    //only want public methods that start with 'get' or 'is'
120:                    //and have no args, and return a value
121:                    final int mask = includeFinalMethods ? Modifier.PUBLIC
122:                            : Modifier.PUBLIC | Modifier.FINAL;
123:                    if (((methods[i].getModifiers() & mask) == Modifier.PUBLIC)
124:                            && (methods[i].getParameterTypes().length == 0)
125:                            && (!methods[i].getName().equals("<init>"))
126:                            && (!methods[i].getName().equals("<clinit>"))
127:                            && (methods[i].getReturnType() != void.class)) {
128:                        final int fieldIndex = this .methods.size();
129:                        addToMapping(methods[i], fieldIndex);
130:                    }
131:                }
132:            }
133:
134:            /**
135:             * Convert it to a form so we can load the bytes from the classpath.
136:             */
137:            private String getResourcePath(final Class clazz) {
138:                return "/" + clazz.getName().replace('.', '/') + ".class";
139:            }
140:
141:            /** 
142:             * Return a list in order of which the getters (and "is") methods were found.
143:             * This should only be done once when compiling a rulebase ideally.
144:             */
145:            public List getPropertyGetters() {
146:                return this .methods;
147:            }
148:
149:            /**
150:             * Return a mapping of the field "names" (ie bean property name convention)
151:             * to the numerical index by which they can be accessed.
152:             */
153:            public Map getFieldNames() {
154:                return this .fieldNames;
155:            }
156:
157:            /**
158:             * @return A mapping of field types (unboxed).
159:             */
160:            public Map getFieldTypes() {
161:                return this .fieldTypes;
162:            }
163:
164:            /** 
165:             * @return A mapping of methods for the getters. 
166:             */
167:            public Map getGetterMethods() {
168:                return this .methodNames;
169:            }
170:
171:            private void addToMapping(final Method method, final int index) {
172:                final String name = method.getName();
173:                int offset;
174:                if (name.startsWith("is")) {
175:                    offset = 2;
176:                } else if (name.startsWith("get")) {
177:                    offset = 3;
178:                } else {
179:                    offset = 0;
180:                }
181:                final String fieldName = calcFieldName(name, offset);
182:                if (this .fieldNames.containsKey(fieldName)) {
183:                    //only want it once, the first one thats found
184:                    if (offset != 0 && this .nonGetters.contains(fieldName)) {
185:                        //replace the non getter method with the getter one
186:                        removeOldField(fieldName);
187:                        storeField(method, index, fieldName);
188:                        this .nonGetters.remove(fieldName);
189:                    }
190:                } else {
191:                    storeField(method, index, fieldName);
192:                    if (offset == 0) {
193:                        this .nonGetters.add(fieldName);
194:                    }
195:                }
196:            }
197:
198:            private void removeOldField(final String fieldName) {
199:                this .fieldNames.remove(fieldName);
200:                this .fieldTypes.remove(fieldName);
201:                this .methods.remove(this .methodNames.get(fieldName));
202:                this .methodNames.remove(fieldName);
203:
204:            }
205:
206:            private void storeField(final Method method, final int index,
207:                    final String fieldName) {
208:                this .fieldNames.put(fieldName, new Integer(index));
209:                this .fieldTypes.put(fieldName, method.getReturnType());
210:                this .methodNames.put(fieldName, method);
211:                this .methods.add(method);
212:            }
213:
214:            private String calcFieldName(String name, final int offset) {
215:                name = name.substring(offset);
216:                return Introspector.decapitalize(name);
217:            }
218:
219:            /**
220:             * Using the ASM classfield extractor to pluck it out in the order they appear in the class file.
221:             * @author Michael Neale
222:             */
223:            static class ClassFieldVisitor implements  ClassVisitor {
224:
225:                private Class clazz;
226:                private ClassFieldInspector inspector;
227:                private boolean includeFinalMethods;
228:
229:                ClassFieldVisitor(final Class cls,
230:                        final boolean includeFinalMethods,
231:                        final ClassFieldInspector inspector) {
232:                    this .clazz = cls;
233:                    this .includeFinalMethods = includeFinalMethods;
234:                    this .inspector = inspector;
235:                }
236:
237:                public MethodVisitor visitMethod(final int access,
238:                        final String name, final String desc,
239:                        final String signature, final String[] exceptions) {
240:                    //only want public methods
241:                    //and have no args, and return a value
242:                    final int mask = this .includeFinalMethods ? Opcodes.ACC_PUBLIC
243:                            : Opcodes.ACC_PUBLIC | Opcodes.ACC_FINAL;
244:                    if ((access & mask) == Opcodes.ACC_PUBLIC) {
245:                        if (desc.startsWith("()") && (!name.equals("<init>"))
246:                                && (!name.equals("<clinit>"))) {// && ( name.startsWith("get") || name.startsWith("is") ) ) {
247:                            try {
248:                                final Method method = this .clazz.getMethod(
249:                                        name, (Class[]) null);
250:                                if (method.getReturnType() != void.class) {
251:                                    final int fieldIndex = this .inspector.methods
252:                                            .size();
253:                                    this .inspector.addToMapping(method,
254:                                            fieldIndex);
255:                                }
256:                            } catch (final NoSuchMethodException e) {
257:                                throw new IllegalStateException(
258:                                        "Error in getting field access method.");
259:                            }
260:                        }
261:                    }
262:                    return null;
263:                }
264:
265:                public void visit(final int arg0, final int arg1,
266:                        final String arg2, final String arg3,
267:                        final String[] arg4, final String arg5) {
268:                }
269:
270:                public void visitInnerClass(final String arg0,
271:                        final String arg1, final String arg2, final int arg3) {
272:                }
273:
274:                public void visitField(final int access, final String arg1,
275:                        final String arg2, final Object arg3,
276:                        final Attribute arg4) {
277:                }
278:
279:                public void visitAttribute(final Attribute arg0) {
280:                }
281:
282:                public void visitEnd() {
283:                }
284:
285:                public void visit(final int arg0, final int arg1,
286:                        final String arg2, final String arg3,
287:                        final String arg4, final String[] arg5) {
288:
289:                }
290:
291:                public void visitSource(final String arg0, final String arg1) {
292:
293:                }
294:
295:                public void visitOuterClass(final String arg0,
296:                        final String arg1, final String arg2) {
297:
298:                }
299:
300:                public AnnotationVisitor visitAnnotation(final String arg0,
301:                        final boolean arg1) {
302:
303:                    return new ClassFieldAnnotationVisitor();
304:                }
305:
306:                public FieldVisitor visitField(final int arg0,
307:                        final String arg1, final String arg2,
308:                        final String arg3, final Object arg4) {
309:
310:                    return null;
311:                }
312:
313:            }
314:
315:            /** 
316:             * This is required for POJOs that have annotations. 
317:             * It may also come in handy if we want to allow custom annotations for marking field numbers etc.
318:             */
319:            static class ClassFieldAnnotationVisitor implements 
320:                    AnnotationVisitor {
321:
322:                public void visit(final String arg0, final Object arg1) {
323:                }
324:
325:                public void visitEnum(final String arg0, final String arg1,
326:                        final String arg2) {
327:                }
328:
329:                public AnnotationVisitor visitAnnotation(final String arg0,
330:                        final String arg1) {
331:                    return new ClassFieldAnnotationVisitor();
332:                }
333:
334:                public AnnotationVisitor visitArray(final String arg0) {
335:                    return new ClassFieldAnnotationVisitor();
336:                }
337:
338:                public void visitEnd() {
339:
340:                }
341:
342:            }
343:
344:        }
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